Anal Mathematics
by Spagthesis
Summary: A story that takes ten years into the future. Lincoln tutors Lily on math while simultaneously letting his sexual urges go haywire. Warning: This one is absolutely ridiculous. Rated M for highly lewd and totally inappropriate.


**Author's note: A highly inappropriate, goofy and disturbing lewd. Based off a joke idea I had, yet I pushed myself to write this anyways. I honestly don't know what's more ridiculous, this or Baking The Cake. Originally posted on my pastebin on 1/13/18.**

* * *

Currently, Lily Loud was a 12 year old sixth grader living with her 22 year old employed brother, Lincoln. She's moved in with him in order to give their parents the freedom they always secretly desired. The fact that they weren't getting any younger sure didn't help, they needed any stress lifted off their shoulders. All those years of raising eleven children wore them out. Despite that, they still lived in the same home and weren't too far away in case their kids needed anything.

Of course, there was something going on between the two siblings. Some frowned upon, incestuous love making took place in these apartment walls. Lincoln's regular relationships with women seemed to fail in the past few years to the point where he essentially just gave up. He only truly loved his family at this point and nobody else. However, he held Lily the dearest.

There has always been an interest of incest lingering somewhere deep inside him. It began at a young age from the simple joys of getting peeks of any of his sisters changing. Eventually, it progressed further. Even while he dated Ronnie Anne, he'd double take at the developing bodies of Lori, Leni, Luna and Luan.

Lily became his prime option due to the fact that she lived with him. Aside from what he's been doing to her, she's the baby of the family. He was more obligated to protect her as any of his siblings would.

Although, she's also at the start of puberty herself. The first noticeable sign, her growth. She was one of the taller girls her age, and pretty slender as well. Strangely enough, her rear grew pretty large, she appeared to be following the steps of her sisters Lori and Luna, who both developed quite fearsome rumps over the years.

If she ended up like the twins, who seemed to have the both of best worlds, Lincoln would have hit the jackpot. Granted, he was grateful for her what she already possessed.

Following many months of living with Lily, simple bonding eventually led to things going further.

Lincoln's only done oral and anal with her so far. He intended to keep it that way for the time being as well as obviously keeping it between them. He had no idea what his family would to do to him if they found out, but he only assumed the worst for good reason.

Aside from that, his high libido never stopped him from getting some regardless of what his little sister was doing. No matter the task she performed, he'd be inclined to capitalize whenever he felt in the mood.

In the present, Lily was doing homework while laying stomach down on her bed, attempting to complete some math equations. It was due the following school day so she got determined to finish it now. Unfortunately, math is her weakest subject, but she felt eager to improve on it as well as maintain all of the good grades she held. She certainly needed some assistance though, and she knew just who to ask for it.

"Lincy, can you help me with my homework?" Lily requested.

Hearing her sweet voice echo through the thin walls of the apartment, Lincoln made his way to her room.

When he got there, he saw her kicking her feet back and forth nervously while biting her lip in frustration.

Lincoln went over and took a seat on the bed, scooting right behind her as she stared hopelessly at her paper.

His intentions were good, mostly, but he was a bit distracted on the dot.

Her rear jiggled like jello each time she kicked her legs. He could see the movement vibrating under her purple skirt.

Lincoln couldn't handle the temptation. He never felt proud of his urges, though he hardly ever actually fought them back.

As he leaned over to see what she was working on, he crept a hand up her thigh.

Lily sensed his warm touch immediately.

She ceased her movement and looked over her shoulder to face him.

Right as she did, he dragged his hand to one of her cheeks and gave it a rough slap, causing the mound of skin to shake intensely from the impact.

"Ahh!" Lily squeaked upon feeling it. Knowing how he's been lately, she should have saw it coming.

After leaving a red mark on her butt cheek, Lincoln smirked devilishly at her.

"Come on, Lincy, this is serious!" She complained.

"I am serious." He said, cracking a smile as his hand now caressed her left butt cheek.

"I have a quiz on this stuff tomorrow and I'm doomed to fail if you don't help me." Lily muttered. Despite paying attention to class lectures, she always tended to struggle with mathematics. She just barely got introduced to the new section of the chapter, and the fact that she's already going to be quizzed on it wasn't doing her any favors.

"Alright, let me see it." Lincoln said, looking over her shoulder.

The young girl handed the piece of paper to him.

Lincoln got a solid look at what she was dealing with. Good 'ol dividing fractions. Math was one of his best subjects, but it had been a while since he had to actually do it himself.

It only required a few seconds of searching in his brain to remember how to solve them. They were fairly easy for him even when he did them at her age.

The man gave her the answer to the first question on the dot. "That one is two thirds." He stated, pointing to the problem.

"How do you know that?" Lily asked.

"Oh, well, I..." He uttered, attempting to explain. It annoyed him back then even, but 'show your work' is a main rule for solving any math problems. Even if you were sharp enough to do it in your head like him, teachers still expected you to break down the equation.

Lily remained fixated on him knowing the answer. She tried to figure out how he did it, yet it wasn't coming to her.

After recovering from what felt like ages, Lincoln spoke again to guide her through the steps. "Flip that second fraction upside down."

Lily did as told and started rewriting the fractions down.

While doing so, her brother kept his other hand busy by resting it on her butt.

Once again, she could feel what he was doing. Normally, they saved this type of thing before going to sleep. Not to mention, she's hardly in the mood for sex due to stress.

"Lincoln..." She mumbled faintly.

The man could hear the annoyance in her tone.

"Sorry, we just haven't done it in a few days..." He mentioned, blushing in embarrassment.

"Fine, go ahead, but if I fail my quiz tomorrow I'm blaming you." Lily said spitefully.

"I'll make sure you don't." Lincoln promised, grinning. In the face of the thrill he was about to seek, he felt really determined to stay true to his word. Her math grade plummeting wasn't something either of them wanted.

From there on, he pulled down her panties, tossing them over towards the top of bed next to all of her pillows.

Lily detected a relaxing mini breeze brush against her as she was now bottomless.

He groped her cheeks thoroughly, then slipped his index finger into her hole.

"Ooh." She moaned, twitching as she felt him press her sphincter.

Feeling her anal walls caused Lincoln's current chub to rise into a full erection.

Looking to get things under way, he took his pants and boxers off, kicking them off the edge of the bed.

The man moved his body over back and mounted his little sister from behind, taking a moment to position himself properly.

He used one hand to hold himself up, and the other to guide his member to her rear.

Lincoln pushed his pelvis down and in a matter of seconds, he allowed the tip of his penis to dig inside her.

Feeling the strain of penetration, the girl tightened her legs. She had gotten use to him going in raw over the months, but the pain still remained, yet it wasn't nearly as bad as the first time they did this. Her hole became slightly looser as time went on, making those insertions just a tad easier to deal with.

Maintaining his momentum, he went deeper as he resumed helping her.

"Alright, multiply both of those fractions, then simplify if you can." He heaved while burying his rod inside her.

Lily bit her lip as she began to multiply. The numbers were fairly small luckily, so she had no trouble with them whatsoever.

As she did that, Lincoln held onto her, trying to keep things steady. The first plunge was always the hardest.

With her hole filled, she finished and received the same answer she was told before.

Noticing that, he asked the most important question, the one that could make or break the equation. "So, can you divide that?"

Lily became a bit surprised by the question, but after looking at it she realized why he asked it.

"No." She said. Or course, he literally gave the answer earlier, though he wanted to acknowledge the last step of solving these equations.

"That's right, but when you get the really big answers you gotta divide them as small as you can."

"Oh..." Lily responded, beginning to understand it somewhat. Even then, that was just the first problem. The rest of them would be more difficult.

Finishing that one, Lincoln then started slowly bucking his hips, thus penetrating inside her as she moved on to the next problem.

"Remember how we did the first one? Just do the same thing. It's really easy when you get the hang of it." He assured during thrusts. All of the multitasking he did as a kid seemed to currently work wonders for him.

During assisting Lily, Lincoln got set into a steady rhythm.

He humped her slowly as he ran his fingers through her soft blonde hair, practically petting her and hoping to soothe any pain she felt due to him.

She experienced uneasiness, and not necessarily because she had her butt stuffed. His weight on top of her along with his warm breath hitting her neck in panting spurts became rather annoying.

Regardless, Lily kept working, following the way her brother showed her.

She was able to solve the next few on her own.

Until, she commenced running into the problems containing larger numbers, causing her to pause when she reached the tenth equation.

Lily did the first step of flipping the fraction, but got lost as soon as she tried to multiply.

Lincoln noticed right away and inquired. "You remember how to multiply big numbers, right?"

"No, I forgot, can you show me?" She asked innocently.

"Alright, let me see your pencil real quick." Lincoln said.

Lily handed it over to him.

The man clenched it in his hands, then he hunched over to reach her paper, sending all of his weight forward, and piercing her greatly.

His testicles pulsated as they rested on her buttocks.

Lincoln let out a grunt while doing his magic on something other than her insides.

He commenced solving the multiplication problem step by step.

"Multiply all of them individually, carry the first number over..." He rambled as he guided Lily yet again. Back when she actually had to multiply regularly, she would stay after school with an actual tutor. Luckily, her big brother was just as helpful.

After blabbering into her ear for a little while longer, it started clicking for her.

She managed to divide and simplify the larger fractions on her own.

Lincoln basically watched her do everything else without assistance. He only planned to speak if she asked for anything, but from the looks of it, she really had it down.

Taking note of that, he shifted his focus back to her behind. He still needed to cum. His semen had built up into something fierce. When he's ready, he's going to have a ton to douse her with, and thinking about it made him eager to get it done.

That in mind, Lincoln kicked his speed up by double, pounding his hips down onto her faster and harder with each thrust.

He could hear and feel his balls slap against her butt, causing the skin to redden.

Lily's moans reoccurred, becoming louder from each pounding she received, and she even nearly dropped her pencil at one point due to it.

Yet, she powered through, and finally made it to the last problem.

The girl rushed right through it, getting the reciprocal, multiplying, dividing and simplifying all in that order.

She lifted her pencil up almost victoriously as she reached the final answer.

"All done!" Lily exclaimed happily.

"S-so, am I." Lincoln huffed as he pulled out of her, promptly seeing the huge gape he gave her. As much as he loved coating that hole with his seed, he decided to go for the next best thing.

He staggered up off the bed and made his way directly in front of her.

Right before Lily put away her finished homework, she saw his large, reddened member lingering in front of her face.

"Open up." He said, temporarily regaining his breath while standing before her.

Lily obeyed, opening her mouth as wide as she could.

Lincoln got a clear view of the inside of her throat.

Knowing she'd swallow, he got right to it, resting his penis head on her bottom teeth.

He massaged his rod roughly, allowing moans to echo from him as he pleasured himself.

When he finally reached his peak, an entire wave of warm semen burst out of his penis.

The flow of liquid stained Lily's tongue and made its way into her throat.

The girl went with her instinct and swallowed. She had gotten use to doing it lately, so it came naturally as did he. Plus, she didn't have anywhere to really spit it out if she wanted to, having felt it was better to gulp it down instead of making a mess. A bitter taste as always, yet the smooth enough texture allowed it to be consumed effortlessly.

"That's my girl!" Lincoln praised.

Afterwards, he gathered his clothes and hurried back to his room, only to pass out almost immediately upon arrival. Working all day and ending his nights with sex often shot his energy.

Lily wiped her mouth once he left, letting out a small chuckle at how ridiculous her brother could be. She wasn't keen on having sex previously, but things seemed to work out just fine. She couldn't really complain knowing how she got the help she wanted.

Finishing everything up, she put her undies back on and let out a yawn.

She laid down on her sex reeked bed, managing to sleep peacefully moments later.

* * *

The day of the quiz had come.

The two siblings woke up and completed all of their morning rituals just a half hour after 7am. Showering, brushing their teeth, getting dressed for their day, things like that. Now, they only had to take care of breakfast.

Normally, Lincoln would cook for the two of them, but he decided to settle with some cereal this morning, finding it more convenient at the time.

Lily made it to the kitchen and sat at the table.

When she scooted herself up closer to the edge, she noticed Lincoln had already eaten as there was an empty bowl across from her.

Spotting her sitting down, the man made his way over to her. He had something else in mind to go along with her breakfast.

Right before she dove into her cereal, she felt something hovering by her.

Lincoln had his cock whipped out into her personal space.

The girl certainly understood what he wanted right away, yet found herself somewhat in disbelief. Especially seeing how big the load he shot in her mouth was yesterday. How is he still horny?

"Lincy, it's too early for that, plus, I just took a shower!" Lily complained.

"It's for good luck." Lincoln said, keeping his stance as his member nudged her shoulder.

"Remember what I said yesterday? I meant it."

"You'll do fine, I mean, especially after we do this." He stated, letting that devilish smirk of his shine.

Through a sigh, Lily went along, fulfilling his lewd desires.

She got up and allowed Lincoln to become her new seat.

Right when he sat down, the young girl dropped her panties and hiked her skirt up, backing herself up in front of him to get into position.

Without turning around, Lily pulled her hand back and gripped his penis.

The sudden touch of her soft, warm hand caused a groan to escape his lips.

Holding his piece in her hand, she stumbled back a bit and began to lower herself, soon feeling his tip press against her anus yet again.

She inhaled deeply as she inserted it slowly. The pain of being pierced always felt unpleasant, but she dealt with it anyways.

Lily managed to take his entire length, leaving her rather large butt cheeks resting straight on his pelvis.

Seeing them vulnerable, Lincoln kneaded them, letting his fingers sink into the plump flesh.

His skin caressed them carefully as his member rested inside of her just like last night. Her walls were a bit easier to handle as they engulfed his whole penis once again. Each time they did anal, he could almost feel her becoming relatively looser down there.

He slumped in his seat, shifting his weight up.

Her cheeks jiggled wildly as he drilled her from his awkward position.

Lily remained as calm as possible while she ate her breakfast.

Occasionally, a moan or a grunt would make its way out of her.

She noted to herself that doing this early in the morning was just as ridiculous as last night. Having sex with her brother being taboo as is, but things could always get stranger no matter what it seemed.

They didn't have too much time for this, so Lincoln rushed his love making.

His hips moved hastily while the noise of her hole getting stretched and their skins slapping heightened.

Right as she finished her cereal, he started losing it. Every second he pumped into her, the closer he became to blowing his load. There wasn't going to be any pulling out either. With each sexual encounter he had, he always had to dispense his seed properly. Orally or anally, either way being good enough for him.

"Guhh." Lincoln grunted, coming inside her.

His testicles strained as they were drained of his semen, pouring out in a gushing amount straight into Lily's rear.

Her legs trembled as she felt the warm liquid slide into her body. This wasn't first time, not even the second or third, though it always managed a similar reaction out of her.

Feeling the cease of movement, Lily knew he finished and lifted herself up off his penis.

An audible wet pop was heard as she stood and hunched over the table.

The feeling of the rough exit caused her to whimper.

Before she recovered, Lincoln rose and pulled the girl's underwear up, wedging his cum inside her.

"Lincy!" Lily pouted.

"It's for good luck." He insisted again.

She already felt uncomfortable, and usually when he did that, she'd be able to go clean it out right away.

Getting what he desired, Lincoln glanced at his watch and witnessed the time. It was a quarter after 8, she had to be there by the half hour mark or else she'd be late.

"Alright, let's get going." He said urgently, zipping his slacks back up and tossing both of their bowls into the sink before heading to the door.

Lily grabbed her backpack and followed behind, walking at a leisurely pace as she tugged at her underwear. This feeling was going to take some getting use to. Today will be a very long day.

Making it outside, Lincoln got into his car and started it up quickly.

Lily opened the passenger side, planting herself in the seat.

When he reversed out of their driveway, she then nervously crossed her legs, keeping them that way and remaining silent on the way there.

After driving through the semi busy roads of Royal Woods, Lincoln got to the school and temporarily parked as close as he could to the main entrance.

"Aren't you forgetting something?" He asked when she attempted to get out.

Realizing what he expected, Lily leaned over and kissed him on the lips. She wasn't always enthusiastic about the sex, but something like kissing was completely sweet and heartwarming to her. It's the one form of affection she never hesitated about.

Following the brief smooch, Lincoln continued. "Don't clean yourself up until you get home, alright?" As vile as it is, he wanted her to keep his load inside her throughout the school day.

The girl sighed, thinking this is going to be pretty rough.

"Bye." She responded, walking away a bit peeved.

Lincoln then drove forward over to his job to endure another dull day of work.

As he left, Lily looked ahead, noticing her friend Melissa waited for her fairly close to the curb.

"Hey, was that your Dad? He's really cute!" The girl exclaimed as she approached her.

Lily sensed her skin chill like ice.

Figuring that her friend must have witnessed them kiss, she went along with the assumption. "Oh, y-yes! That's my Daddy." She replied.

From there on, the two young girls walked to their class together.

They both made it three minutes before class officially began.

Lily panned around the room and headed for her assigned seat. It was way in the back on the far right side. A preferred area for her seeing how the thought of being in the front right under the teacher's nose intimidated her greatly.

She took her seat and blushed still feeling Lincoln's semen flowing around her punished hole. Hopefully, it would provide her good luck because all it did so far was make her incredibly embarrassed. It would dry pretty soon, but she's still gonna have to toss her undies in the laundry pile when she gets home.

Until then, she sat quietly, staring up front while waiting for class to begin.

The bell soon rang as everyone got seated and ready to begin. Math was up first, the rest of subjects along with recess and lunch would come later.

Right off the bat, Mrs. Sander greeted the class, reminding them of the quiz that was about to take place.

After speaking briefly, she went around the whole class and collected their homework as well as handed the quizzes out.

Lily received her quiz last. Some of her peers worked fast, other were slow due to struggling a bit. The latter she could relate to, especially before Lincoln helped her.

Thanks to him, she found herself having little to no trouble with the equations. She recalled everything he lectured her on last night.

Making sure she showed her work, Lily commenced solving all the fractions.

The first few were relatively simple, but as she progressed they became a bit more challenging, using some larger numbers as opposed to smaller, pretty much resembling the homework she just turned in.

Lily couldn't multiply the double digits problems in her head like Lincoln, yet she was able to solve it as he explained it.

While following every step and showing her work, her speed picked up.

Not the first or last, but soon, Lily stood up and walked to her teacher's desk.

Her rear shook immensely with each step she took, despite the passing of time, she felt like she could still feel Lincoln's cum as if it was freshly shot. She had an almost permanent blush on her face any time she moved a muscle.

Following handing her test to Mrs. Sander, she became a bit stressed upon thinking about the mistakes she might have made on there. It would devastate her if she failed. Granted, her pessimistic thoughts at times were normally just her mind exaggerating. Things never really turned out too bad for her.

Lily returned to her seat.

And once again, sitting down made her feel so awkward. She knew there was a huge stain on her panties. She needed to survive the rest of the day with it as well as hope she doesn't have to bend over and potentially expose herself for any reason.

The rest of the educational day resumed as usual. Recess, lunch and her other main classes were held soon after.

Hours passed until she was finally on the verge of leaving, and receiving her graded quiz.

She could feel herself sweating in anticipation while she gripped her hands together like in the form of a prayer.

Mrs. Sander slowly walked in circles around the classroom, handing over quizzes to the correct students.

Their expressions varied on many levels, reactions of disappointment or joy seemed to infect everybody.

Shortly later, she came by Lily and handed her paper over.

The girl grabbed it, bringing it too close to her face on accident.

Although, she definitely saw her grade clear as day.

Lily let out a big sigh of relief. Anxiety built up inside her ever since she turned it in, but the final result satisfied her.

Then the school dismissal bell rang blared. A two day vacation will soon follow and she felt pretty eager for it. Especially with how well things turned out for her, and to top it all off, no homework for the weekend. Regardless, she just couldn't wait to show Lincoln her quiz results.

Lily got up and followed the other kids out the door. Her destination was the parking lot where the school buses were. Taking the bus home became normal for her, seeing how her brother worked late and wasn't able to pick her up.

As she made it on board, she sat down next to one of the open windows.

She glanced at her final grade one last time before putting the quiz in her backpack.

Once again, Lily's mind seemed to assume the worst. She imagined the paper slipping out of her grip and flying straight out of the window. She needed the solid evidence to show Lincoln. That said, he always trusted her word. She wasn't one to really lie about anything, unless it involved something along the lines of what her relationship with him was.

Once everyone else made it, the bus driver drove off.

During the way, Lily remembered what she needed to do first when she gets home. Clean herself up.

While fixated on those thoughts for the short ride, the girl reached her stop.

Getting off the bus, she walked a few blocks to reach home.

During the way, feeling self conscious about her butt encouraged her to move faster.

When Lily made it to the apartment building, she unlocked the door and darted inside.

She ran to her room and stripped her underwear off in a mere second, frowning noticing the stain on her purple panties. A huge pool of dried semen coated the entire middle of them, gross.

Seeing that, she searched around her dresser for a clean pair, then went and threw the other into the pile of dirty clothes.

Before she put them on however, Lily walked to the bathroom to wipe her bottom clean. It bugged her the entire day, and finally taking care of it brought her great relief.

While she chilled for the next two hours, the clock struck 5pm.

Lincoln would be home from work soon. Luckily for him, he was always guaranteed weekends off, so he felt determined to get home as soon as he could. Lily remained on his mind all day at work, and he hoped for some great news when he came.

Ten minutes later, he pulled into the driveway.

Lily became ecstatic when she saw him leaving his car and heading on up to the door.

As arrived inside, she stood before him smiling with her hands behind her back.

"Hey, sweetie, did you pass?" He asked immediately as he faced her.

Judging from the radiant look she gave him, he figured she did.

Lily grinned while she revealed the paper from behind her back.

She brought it around, holding it high to reach Lincoln's eye level and beaming pridefully as she awaited his reaction.

The quiz had a huge red a written on top it accompanied with a small smiley face. She appeared to have only missed about two answers, not that it really mattered.

"Good job, Lily, I knew you could do it!" Lincoln praised. The fact that he was able to help her with something like this warmed his heart. Granted, he knew she's a smart kid, and he dare not intend to take credit for something she accomplished. Nonetheless, part of him wanted to laugh as he wondered if maybe the cum he left inside her this morning actually was good luck.

Breaking those thoughts off, he asked her the only other thing he could think of for today. "So, what would you like your dinner?" After seeing her good work, he figured he should reward her by letting her choose whatever she wanted. She's definitely earned the privilege.

"Hmm..." Lily mused briefly.

"You can have anything you want." Lincoln assured contently.

"Anything?" She questioned, looking him straight in the eyes. A sincere offer she just couldn't refuse.

"Anything for you."

"I think I know a place." Lily said, smiling radiantly and reaching her hand out to him.

Lincoln held her hand as he led the way back to his car. He wasn't keen on going out to eat seeing how expensive it could be, mainly because he was barely making ends meet. Yet, he felt she deserved whatever she wanted especially after putting up with his sexual urges in recent times.


End file.
